How to Create a SWC Library from Your AS3 Code

Problem: Create a SWC library from your existing AS3 code. A SWC library is a pre-compiled file of classes and (optionally) graphical assets. They are useful for creating themes (see Creating Themes), distributing an application without distributing its source code, or for creating a compressed copy of your code library. As an example, the Flare library ships with a pre-compiled SWC that contains the entire library in one SWC file. If you’re worried about efficiency, compiling against a SWC library works exactly the same as compiling from source: only classes that you actually use are included in your final SWF. If you have a reusable code base that you want to compile into a single file, SWC’s are for you.

Solution: Flex Ant tasks.

This post assumes that you have Flex and Ant already installed. You can find the Flex installation page here and the Ant home page here. (If you’d be interested in a tutorial covering Flex/Ant, installation, please post a comment).

All you need to compile a SWC file containing your AS3 code is a build.properties file, a build.xml file, and, of course, a directory containing your code. First we’ll cover the contents of these files, then we’ll talk about how to use them in conjunction with Ant.

The ‘build.properties’ file is a simple text file that contains the configuration options for your SWC library. The following build.properties file will take all the code in the ‘myCode’ directory and compile it into a single SWC file called ‘library.swc’. Remember to change ‘FLEX_HOME’ to the path where you installed Flex.

build.properties is the actual file (right-click and select “Save Link As…”).

The ‘build.xml’ file contains the commands that Ant will actually run. For a detailed interpretation of this file, refer to Flex Ant Tasks. You shouldn’t need to change this file, aside from adding a few more ‘‘ lines for advanced options (you’ll have to consult the Compc Reference or the Mxmlc Reference for a list of compiler arguments. A few common arguments like ‘-target-player’ are included, but commented out.

build.xml is the actual file (right-click and select “Save Link As…”).

To use these files with Ant, download both of them and copy them into one directory above where your code library resides. In the example, this is the directory containing the ‘myCode’ folder (not the ‘myCode folder itself). Open a console and change to the directory containing build.xml and build.properties. Now run the ‘ant’ command. Simply type the following into the console:

The console should print ‘Generating SWC Library,’ along with some other technical details, and then you should have a nice new SWC appear in that same folder.

If you experience some compiler errors, remember that the ENTIRE library is being compiled, so it needs a path to EVERY other external AS3 file that the library references. For example, if you are compiling something that requires the Flare library, you will need to give add an argument in ‘build.xml’ that points to the Flare library source on your computer. Otherwise, you will get a seemingly endless list of errors. This can be done with either of the following lines:

Now, you might be asking, how do I actually use a SWC file within an application? Well, if you have Flash CS4, you can add a path to the SWC under ‘Publish Settings->ActionScript3.0 Settings…->External Library Path’. I’m not sure if this works in Flash CS3, but you can definitely save your external SWC into ‘Adobe Flash CS3\Common\Configuration\Components’, where ‘Adobe Flash CS3‘ is your Flash installation directory. Then, the classes in these SWC files will be available in the Flash IDE. This method will also work in Flash CS4. In short, compiling against a SWC file is essentially the same as compiling against AS3 source files, you just have to tell Flash where to look for the SWC file.

This tutorial was meant to be a quick introduction to using Flex and Ant. Creating SWC code libraries is only one of the many uses of the Flex compilers. It is by no means a comprehensive overview of Flex Ant Tasks. If you would like to see a more detailed tutorial about Flex and Ant, please post a comment below. For now, please refer to Using the Flex Compilers from Adobe.